1. Field of the Invention
The present invention relates to a printing system and a printing method.
2. Description of the Related Art
There has been known a printing system disclosed in, for example, Japanese Patent Application Laid-open No. 321062/1992, in which a sheet reversing device is interposed between printers disposed adjacent to each other, a toner image is fixed to one surface of a sheet by the printer located at a front stage with respect to the sheet reversing device, the fed sheet is reversed by the sheet reversing device, the sheet is fed to the printer located at a rear stage with respect to the sheet reversing device, the toner image is fixed to the other surface of the sheet, and thus, the toner images are formed at both surfaces of the sheet (the above-described mode of the printing system will be hereinafter referred to as “a tandem printing system” for the sake of convenience).
In the tandem printing system as described above, when the toner image is fixed to the recording medium in the printer at the front stage, there has arisen a problem of heat shrinkage of the recording medium by heating operation of the fixing device. Consequently, when a finally obtained printout having images on both sides thereof is seen through, a region printed by the printer at the front stage cannot completely overlap with a region printed by the printer at the rear stage. In the case where double-sided printing is performed with respect to a thin sheet for use in, e.g., a dictionary, there may be caused inconvenience of formation of a printout of bad appearance in which intervals between characters or lines cannot completely overlap with each other at first and second surfaces.
Furthermore, in one of printing systems of this type, in order to achieve high-speed and large-volume printing, a sheet having, e.g., a width of 18 in. (a length in a direction perpendicular to a sheet feeding direction) and a length of 11 in. (a length in the sheet feeding direction) is used as the recording medium, an image on a first page and an image on a second page are arranged on the sheet in the sheet width direction, and finally, the sheet is cut into two sheets of a letter or A4 size, thus obtaining two pieces of printouts (like this example, printing the images of two pages in arrangement may be referred to as “2-up printing”).
Also in the case where the above-described 2-up printing is performed in combination with the above-described tandem printing, the sheet is shrunk by about 2 mm in the width direction and by about 1 mm in the length direction in the fixing process in the printer at the front stage, thereby arising a problem that a printing position by the printer at the rear stage cannot completely overlap with a printing position by the printer at the front stage, as described above.
Incidentally, the above-described problems are not peculiar only to the above-described tandem printing system, and they are liable to arise also in the configuration in which no sheet reversing device is interposed between the two printers.